Compositions of 2,4,4,4-tetrafluorobut-1-ene and cis-1,1,1,4,4,4-hexafluorobut-2-ene

ABSTRACT

A composition including 2,4,4,4-10-tetrafluorobut-1-ene and cis-1,1,1,4,4,4-hexafluorobut-2-ene, and also the use thereof in particular as a heat transfer fluid. The composition may include: from 1% to 99% of 2,4,4,4-tetrafluorobut-1-ene and from 1% to 99% of cis-1,1,1,4,4,4-hexafluorobut-2-ene; preferably from 5% to 70% of 2,4,4,4-tetrafluorobut-1-ene and from 30% to 95% of cis-1,1,1,4,4,4-hexafluorobut-2-ene; preferably from 20% to 65% of 2,4,4,4-tetrafluorobut-1-ene and from 35% to 80% of cis-1,1,1,4,4,4-hexafluorobut-2-ene; preferably from 25% to 60% of 2,4,4,4-tetrafluorobut-1-ene and from 40% to 75% of cis-1,1,1,4,4,4-hexafluorobut-2-ene; preferably from 28% to 51% of 2,4,4,4-tetrafluorobut-1-ene and from 49% to 72% of cis-1,1,1,4,4,4-hexafluorobut-2-ene.

FIELD OF THE INVENTION

The present invention relates to compositions of2,4,4,4-tetrafluorobut-1-ene and cis-1,1,1,4,4,4-hexafluorobut-2-ene andto their use, in particular as heat-transfer fluids.

TECHNICAL BACKGROUND

Fluids based on fluorocarbon compounds are widely used in systems forthe transfer of heat by compression of vapor, in particular airconditioning, heat pump, refrigeration or freezing devices. Thesedevices have it in common that they are based on a thermodynamic cyclecomprising the vaporization of the fluid at low pressure (in which thefluid absorbs heat); the compression of the vaporized fluid up to a highpressure; the condensation of the vaporized fluid to give a liquid athigh pressure (in which the fluid discharges heat); and the reduction inpressure of the fluid in order to complete the cycle.

The choice of a heat-transfer fluid (which can be a pure compound or amixture of compounds) is dictated, on the one hand, by the thermodynamicproperties of the fluid and, on the other hand, by additionalconstraints. Thus, a particularly important criterion is that of theimpact of the fluid under consideration on the environment. Inparticular, chlorinated compounds (chlorofluorocarbons andhydrochlorofluorocarbons) exhibit the disadvantage of damaging the ozonelayer. Thus, nonchlorinated compounds, such as hydrofluorocarbons,fluoroethers and fluoroolefins, are from now on generally preferred tothem.

It is also still necessary to develop other heat-transfer fluidsexhibiting a lower global warming potential (GWP) than that of theheat-transfer fluids currently used and exhibiting equivalent orimproved performances.

The document U.S. Pat. No. 5,076,064 describes the replacement oftrichlorofluoromethane (CFC-11) par other refrigerants in centrifugalcompressors. The use of 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123) isin particular provided in this document. However, it remains desirableto use refrigerants which are even less toxic to the ozone layer andwhich exhibit a lower GWP than HCFC-123.

The document WO 2010/141669 describes the use ofcis-1,1,1,4,4,4-hexafluorobut-2-ene (or Z-HFO-1336mzz) as refrigerant,in particular as a replacement for CFC-11 and HCFC-123. However, theperformance of this compound is unsatisfactory. In particular, itsvolumetric capacity is markedly lower than that of HCFC-123.

The document WO 2010/141527 describes azeotropic or quasi-azeotropiccompositions comprising Z-HFO-1336mzz and another compound which can beethanol, 2-chloro-3,3,3-trifluoropropene, methanol,trans-1,1,1,4,4,5,5,5-octafluoropent-2-ene,2-bromo-3,3,3-trifluoropropene, methyl acetate, acetone, chloroform,n-hexane or 1-chloro-3,3,3-trifluoropropene. These mixtures are highlyinflammable and/or are not suitable for the replacement of refrigerantssuch as HCFC-123.

The document WO 2010/100254 describes in a general way the use ofmixtures of fluoroolefins of HFO-1354 and HFO-1336 type. The HFO-1354can be 2,4,4,4-tetrafluorobut-1-ene and HFO-1336 can be HFO-1336 mzz.However, the isomeric form of the latter compound is not specified.

There still exists a need to develop other heat-transfer fluids whichare less toxic to the ozone layer and which exhibit a relatively lowGWP, in order to replace the ordinary heat-transfer fluids.

In particular, it is desirable to develop heat-transfer fluids having alow GWP which can replace HCFC-123 while offering similar, indeedimproved, energy performances, it being possible for the replacementpreferably to be carried out without modifying the existinginstallations or their operating parameters.

SUMMARY OF THE INVENTION

The invention relates first to a composition comprising2,4,4,4-tetrafluorobut-1-ene and cis-1,1,1,4,4,4-hexafluorobut-2-ene.

According to one embodiment, the composition consists of a mixture of2,4,4,4-tetrafluorobut-1-ene and cis-1,1,1,4,4,4-hexafluorobut-2-ene.

According to one embodiment, the composition comprises:

-   -   from 1% to 99% of 2,4,4,4-tetrafluorobut-1-ene and from 1% to        99% of cis-1,1,1,4,4,4-hexafluorobut-2-ene;    -   preferably from 5% to 70% of 2,4,4,4-tetrafluorobut-1-ene and        from 30% to 95% of cis-1,1,1,4,4,4-hexafluorobut-2-ene;    -   preferably from 20% to 65% of 2,4,4,4-tetrafluorobut-1-ene and        from 35% to 80% of cis-1,1,1,4,4,4-hexafluorobut-2-ene;    -   preferably from 25% to 60% of 2,4,4,4-tetrafluorobut-1-ene and        from 40% to 75% of cis-1,1,1,4,4,4-hexafluorobut-2-ene;    -   preferably from 28% to 51% of 2,4,4,4-tetrafluorobut-1-ene and        from 49% to 72% of cis-1,1,1,4,4,4-hexafluorobut-2-ene.

According to one embodiment, the composition is quasi-azeotropic,preferably azeotropic.

The invention also relates to the use of the abovementioned compositionas heat-transfer fluid.

According to one embodiment, the composition is quasi-azeotropic,preferably azeotropic.

According to one embodiment, the composition is nonflammable.

The invention also relates to a heat-transfer composition comprising theabovementioned composition and also one or more additives chosen fromlubricants, stabilizing agents, surfactants, tracers, fluorescentagents, odorous agents, solubilizing agents and their mixtures.

The invention also relates to a heat-transfer installation comprising avapor compression circuit containing the abovementioned composition asheat-transfer fluid or containing the abovementioned heat-transfercomposition.

According to one embodiment, the installation comprises a centrifugalcompressor and preferably a direct-drive centrifugal compressor.

According to one embodiment, the installation comprises a floodedevaporator.

According to one embodiment, the installation is chosen from mobile orstationary installations for heat-pump heating, air conditioning, inparticular motor vehicle air conditioning or centralized stationary airconditioning, refrigeration or freezing and Rankine cycles and ispreferably an air conditioning installation.

The invention also relates to a process for heating or cooling a liquidor a body by means of a vapor compression circuit containing aheat-transfer fluid, said process successively comprising theevaporation of the heat-transfer fluid, the compression of theheat-transfer fluid, the condensation of the heat fluid and thereduction in pressure of the heat-transfer fluid, in which theheat-transfer fluid is a composition as described above.

The invention also relates to a process for reducing the environmentalimpact of a heat-transfer installation comprising a vapor compressioncircuit containing an initial heat-transfer fluid, said processcomprising a stage of replacement of the initial heat-transfer fluid inthe vapor compression circuit by a final transfer fluid, the finaltransfer fluid exhibiting a lower GWP than the initial heat-transferfluid, in which the final heat-transfer fluid is a composition asdescribed above.

According to one embodiment, the initial heat-transfer fluid is2,2-dichloro-1,1,1-trifluoroethane.

The invention also relates to the use of the abovementioned compositionas solvent.

The invention also relates to the use of the abovementioned compositionas blowing agent.

The invention also relates to the use of the abovementioned compositionas propellant, preferably for an aerosol.

The invention also relates to the use of the abovementioned compositionas cleaning agent.

The present invention makes it possible to meet the needs felt in thestate of the art. It more particularly provides novel low-GWPcompositions which are non toxic to the ozone layer and which arecapable of being used (inter alia) as heat-transfer fluids, inparticular as a replacement for ordinary heat-transfer fluids and veryparticularly HCFC-123.

In particular, the invention provides, in some embodiments, azeotropicor quasi-azeotropic compositions.

In some embodiments, the invention provides heat-transfer fluids whichexhibit good energy performances in comparison with ordinaryheat-transfer fluids and in particular in comparison with HCFC-123,especially a similar, indeed even improved, volumetric capacity and/or asimilar, indeed even improved, coefficient of performance. According tosome embodiments, the replacement of HCFC-123 can be carried out withoutmodifying the heat-transfer installation or its operating parameters.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 represents the normal boiling point in ° C. of theZ-HFO-1336mzz/2,4,4,4-tetrafluorobut-1-ene mixture (on the ordinate) asa function of the mass fraction of Z-HFO-1336mzz in the mixture (on theabscissa).

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention is now described in more detail and without impliedlimitation in the description which follows.

Unless otherwise mentioned, throughout the patent application, theproportions of compounds indicated are given as molar percentages.

According to the present patent application, the global warmingpotential (GWP) is defined with respect to carbon dioxide and withrespect to a duration of 100 years, according to the method indicated in“The Scientific Assessment of Ozone Depletion, 2002, a Report of theWorld Meteorological Association's Global Ozone Research and MonitoringProject”.

The term “heat-transfer compound”, respectively “heat-transfer fluid”(or refrigerant), is understood to mean a compound, respectively afluid, capable of absorbing heat on evaporating at low temperature andlow pressure and of discharging heat on condensing at high temperatureand high pressure, in a vapor compression circuit. Generally, aheat-transfer fluid can comprise just one, two, three or more than threeheat-transfer compounds.

The term “heat-transfer composition” is understood to mean a compositioncomprising a heat-transfer fluid and optionally one or more additiveswhich are not heat-transfer compounds for the application envisaged.

The additives can in particular be chosen from lubricants, stabilizingagents, surfactants, tracers, fluorescent agents, odorous agents andsolubilizing agents.

The stabilizing agent or agents, when they are present, preferablyrepresent at most 5% by weight in the heat-transfer composition. Mentionmay in particular be made, among the stabilizing agents, ofnitromethane, ascorbic acid, terephthalic acid, azoles, such astolutriazole or benzotriazole, phenolic compounds, such as tocopherol,hydroquinone, t-butylhydroquinone or 2,6-di(tert-butyl)-4-methylphenol,epoxides (alkyl, optionally fluorinated or perfluorinated, or alkenyl oraromatic), such as n-butyl glycidyl ether, hexanediol diglycidyl ether,allyl glycidyl ether or butylphenyl glycidyl ether, phosphites,phosphonates, thiols and lactones.

Use may in particular be made, as lubricants, of oils of mineral origin,silicone oils, paraffins of natural origin, naphthenes, syntheticparaffins, alkylbenzenes, poly(α-olefin)s, polyalkene glycols, polyolesters and/or polyvinyl ethers.

Mention may be made, as tracers (agents capable of being detected), ofdeuterated or nondeuterated hydrofluorocarbons, deuterated hydrocarbons,perfluorocarbons, fluoroethers, brominated compounds, iodinatedcompounds, alcohols, aldehydes, ketones, nitrous oxide and thecombinations of these. The tracer is different from the heat-transfercompound or compounds making up the heat-transfer fluid.

Mention may be made, as solubilizing agents, of hydrocarbons, dimethylether, polyoxyalkylene ethers, amides, ketones, nitriles, chlorocarbons,esters, lactones, aryl ethers, fluoroethers and 1,1,1-trifluoroalkanes.The solubilizing agent is different from the heat-transfer compound orcompounds making up the heat-transfer fluid.

Mention may be made, as fluorescent agents, of naphthalimides,perylenes, coumarins, anthracenes, phenanthracenes, xanthenes,thioxanthenes, naphthoxanthenes, fluoresceins and the derivatives andcombinations of these.

Mention may be made, as odorous agents, of alkyl acrylates, allylacrylates, acrylic acids, acryl esters, alkyl ethers, alkyl esters,alkynes, aldehydes, thiols, thioethers, disulfides, allylisothiocyanates, alkanoic acids, amines, norbornenes, norbornenederivatives, cyclohexene, aromatic heterocyclic compounds, ascaridole,o-methoxy(methyl)phenol and the combinations of these.

The heat-transfer process according to the invention is based on the useof an installation comprising a vapor compression circuit which containsa heat-transfer fluid. The heat-transfer process can be a process inwhich a fluid or a body is heated or cooled.

The vapor compression circuit containing a heat-transfer fluid comprisesat least one evaporator, one compressor, one condenser and one expansiondevice, and also lines for transporting heat-transfer fluid betweenthese components. The evaporator and the condenser comprise a heatexchanger which makes possible an exchange of heat between theheat-transfer fluid and another fluid or body.

Use may in particular be made, as compressor, of a single-stage ormultistage centrifugal compressor or a centrifugal minicompressor.Rotary, piston or screw compressors can also be used. The compressor canbe driven by an electric motor or by a gas turbine (for example fed bythe exhaust gases from a vehicle, for mobile applications) or by gears.

The installation can comprise a turbine in order to generate electricity(Rankine cycle).

The installation can also optionally comprise at least one heat-exchangefluid circuit used to send heat (with or without change in state)between the heat-transfer fluid circuit and the fluid or body to beheated or cooled.

The installation can also optionally comprise two (or more) vaporcompression circuits containing identical or distinct heat-transferfluids. For example, the vapor compression circuits can be coupled toone another.

The vapor compression circuit operates according to a conventional vaporcompression cycle. The cycle comprises the change in state of theheat-transfer fluid from a liquid phase (or liquid/vapor two-phasesystem) to a vapor phase at a relatively low pressure, then thecompression of the fluid in the vapor phase up to a relatively highpressure, the change in state (condensation) of the heat-transfer fluidfrom the vapor phase to the liquid phase at a relatively high pressure,and the reduction in the pressure in order to recommence the cycle.

In the case of a cooling process, heat resulting from the fluid or bodywhich is cooled (directly or indirectly, via a heat-exchange fluid) isabsorbed by the heat-transfer fluid, during the evaporation of thelatter, this taking place at a relatively low temperature with respectto the environment. The cooling processes comprise air conditioning(with mobile installations, for example in vehicles, or stationaryinstallations), refrigeration and freezing or cryogenic processes.

In the case of a heating process, heat is given up (directly orindirectly, via a heat-exchange fluid) by the heat-transfer fluid,during the condensation of the latter, to the fluid or body which isheated, this taking place at a relatively high temperature with respectto the environment. The installation which makes it possible to carryout the heat transfer is known in this case as a “heat pump”.

It is possible to employ any type of heat exchanger for the use of theheat-transfer fluids according to the invention and in particularcocurrentwise heat exchangers or, preferably, countercurrentwise heatexchangers.

The heat-transfer fluids used in the context of the present inventionare compositions comprising Z-HFO-1336mzz and2,4,4,4-tetrafluorobut-1-ene.

According to one embodiment, these heat-transfer fluids can comprise oneor more additional heat-transfer compounds.

These additional heat-transfer compounds can be chosen in particularfrom hydrocarbons, hydrofluorocarbons, ethers, hydrofluoroethers andfluoroolefins.

According to these specific embodiments, the heat-transfer fluidsaccording to the invention can be ternary compositions (consisting ofthree heat-transfer compounds) or quaternary compositions (consisting offour heat-transfer compounds), in combination with the lubricating oil,in order to form the heat-transfer compositions according to theinvention.

When additional heat-transfer compounds are present, it is preferablefor their total proportion in the above heat-transfer fluids to be lessthan or equal to 20%, or less than or equal to 15%, or less than orequal to 10%, or less than or equal to 5%, or less than or equal to 2%.

According to one embodiment, the heat-transfer fluids are composedessentially of a mixture of Z-HFO-1336mzz and2,4,4,4-tetrafluorobut-1-ene, indeed even consist of such a mixture(binary compositions).

Impurities can be present in such heat-transfer fluids, in a proportionof less than 1%, preferably less than 0.5%, preferably less than 0.1%,preferably less than 0.05% and preferably less than 0.01%.

According to specific embodiments, the proportion of Z-HFO-1336mzz inthe heat-transfer fluid can be: from 0.1% to 5%; or from 5% to 10%; orfrom 10% to 15%; or from 15% to 20%; or from 20% to 25%; or from 25% to30%; or from 30% to 35%; or from 35% to 40%; or from 40% to 45%; or from45% to 50%; or from 50% to 55%; or from 55% to 60%; or from 60% to 65%;or from 65% to 70%; or from 70% to 75%; or from 75% to 80%; or from 80%to 85%; or from 85% to 90%; or from 90% to 95%; or from 95% to 99.9%.

According to specific embodiments, the proportion of2,4,4,4-tetrafluorobut-1-ene in the heat-transfer fluid can be: from0.1% to 5%; or from 5% to 10%; or from 10% to 15%; or from 15% to 20%;or from 20% to 25%; or from 25% to 30%; or from 30% to 35%; or from 35%to 40%; or from 40% to 45%; or from 45% to 50%; or from 50% to 55%; orfrom 55% to 60%; or from 60% to 65%; or from 65% to 70%; or from 70% to75%; or from 75% to 80%; or from 80% to 85%; or from 85% to 90%; or from90% to 95%; or from 95% to 99.9%.

Among the above heat-transfer fluids, some exhibit the advantage ofbeing azeotropic or quasi-azeotropic.

The term “quasi-azeotropic” denotes the compositions for which, at aconstant temperature, the saturated liquid pressure and the saturatedvapor pressure are virtually identical (the maximum difference inpressure being 10%, indeed even advantageously 5%, with respect to thesaturated liquid pressure).

For “azeotropic” compositions, at a constant temperature, the maximumdifference in pressure is in the vicinity of 0%.

Such heat-transfer fluids exhibit an advantage of ease of use. In theabsence of significant glide, there is no significant change in thecirculating composition and no significant change either in thecomposition in the event of leakage.

FIG. 1 represents the normal boiling point of the heat-transfer fluid asa function of the mass proportion of Z-HFO-1336mzz in the mixture. Thecalculation of the normal boiling point as a function of the compositionis based on data measured in the laboratory (temperature, pressure,critical point, liquid/vapor equilibrium, and the like) or estimatedaccording to methods of estimation by group contribution or bycorresponding state. These methods are described in the work “TheProperties of Gases and Liquids”, 5^(th) edition, Bruce E. Poling, andare also available in software, such as ASPEN or ThermoDataEngine(NIST).

Advantageously, the compositions according to the invention arenonflammable, within the meaning of the standard ASHRAE 34-2007, andpreferably with a test temperature of 60° C. instead of 100° C.

In addition, some compositions according to the invention exhibitimproved performances in comparison with some known heat-transferfluids, in particular for moderate-temperature cooling processes, thatis to say those in which the temperature of the cooled fluid or body isfrom −15° C. to 15° C., preferably from −10° C. to 10° C., moreparticularly preferably from −5° C. to 5° C. (ideally approximately 0°C.).

Furthermore, some compositions according to the invention exhibitimproved performances in comparison with some known heat-transferfluids, in particular for moderate-temperature heating processes, thatis to say those in which the temperature of the heated fluid or body isfrom 30° C. to 80° C., preferably from 35° C. to 55° C., or particularlypreferably from 40° C. to 50° C. (ideally approximately 45° C.).

In the “moderate-temperature cooling or heating” processes mentionedabove, the inlet temperature of the heat-transfer fluid in theevaporator is preferably from −20° C. to 10° C., in particular from −15°C. to 5° C., more particularly preferably from −10° C. to 0° C. and forexample approximately −5° C.; and the temperature of the start of thecondensation of the heat-transfer fluid in the condenser is preferablyfrom 25° C. to 90° C., in particular from 30° C. to 70° C., moreparticularly preferably from 35° C. to 55° C. and for exampleapproximately 50° C. These processes can be refrigeration, airconditioning or heating processes.

Some compositions are also appropriate for high-temperature heatingprocesses, that is to say those in which the temperature of the heatedfluid or body is greater than 90° C., for example greater than or equalto 110° C. or greater than or equal to 130° C., and preferably less thanor equal to 160° C.

Some compositions according to the invention exhibit improvedperformances in comparison with some known heat-transfer fluids, inparticular for low-temperature refrigeration processes, that is to saythose in which the temperature of the cooled fluid or body is from −40°C. to −10° C., preferably from −35° C. to −25° C., more particularlypreferably from −30° C. to −20° C. (ideally approximately −25° C.).

In the “low-temperature refrigeration” processes mentioned above, theinlet temperature of the heat-transfer fluid in the evaporator ispreferably from −45° C. to −15° C., in particular from −40° C. to −20°C., more particularly preferably from −35° C. to −25° C. and for exampleapproximately −30° C.; and the temperature of the start of thecondensation of the heat-transfer fluid in the condenser is preferablyfrom 25° C. to 80° C., in particular from 30° C. to 60° C., moreparticularly preferably from 35° C. to 55° C. and for exampleapproximately 40° C.

The compositions according to the invention can be used to replacevarious heat-transfer fluids in various heat-transfer applications, forexample in air conditioning. For example, the compositions according tothe invention can be used to replace:

-   -   1,1,1,2-tetrafluoroethane (R134a);    -   1,1-difluoroethane (R152a);    -   1,1,1,3,3-pentafluoropropane (R245fa);    -   mixtures of pentafluoroethane (R125), 1,1,1,2-tetrafluoroethane        (R134a) and isobutane (R600a), namely the R422 products;    -   chlorodifluoromethane (R22);    -   the mixture of 51.2% chloropentafluoroethane (R115) and 48.8%        chlorodifluoromethane (R22), namely R502;    -   any hydrocarbon;    -   the mixture of 20% difluoromethane (R32), 40% pentafluoroethane        (R125) and 40% 1,1,1,2-tetrafluoroethane (R134a), namely R407A;    -   the mixture of 23% difluoromethane (R32), 25% pentafluoroethane        (R125) and 52% 1,1,1,2-tetrafluoroethane (R134a), namely R407C;    -   the mixture of 30% difluoromethane (R32), 30% pentafluoroethane        (R125) and 40% 1,1,1,2-tetrafluoroethane (R134a), namely R407F;    -   R1234yf (2,3,3,3-tetrafluoropropene);    -   R1234ze (1,3,3,3-tetrafluoropropene).

In addition, the following preferred compositions are very particularlyappropriate for the replacement of HCFC-123:

-   -   from 5% to 70% of 2,4,4,4-tetrafluorobut-1-ene and from 30% to        95% of Z-HFO-1336mzz;    -   preferably from 20% to 65% of 2,4,4,4-tetrafluorobut-1-ene and        from 35% to 80% of Z-HFO-1336mzz;    -   preferably from 25% to 60% of 2,4,4,4-tetrafluorobut-1-ene and        from 40% to 75% of Z-HFO-1336mzz;    -   preferably from 28% to 51% of 2,4,4,4-tetrafluorobut-1-ene and        from 49% to 72% of Z-HFO-1336mzz.

Use may be made, by way of example, of a composition comprisingapproximately 28% of 2,4,4,4-tetrafluorobut-1-ene and approximately 72%of Z-HFO-1336mzz.

This is because, in this case, the average molar mass, as well as theboiling point, of the heat-transfer fluid are very close to the molarmass and the boiling point of HCFC-123. Thus, the composition comprising28% of 2,4,4,4-tetrafluorobut-1-ene and approximately 72% ofZ-HFO-1336mzz exhibits an average molar mass of 152.09 g/mol (against152.93 g/mol for HCFC-123) and a boiling point equivalent to thetemperature of HCFC-123.

Thus, the compositions preferred above make it possible to replaceHCFC-123 without modifying or virtually without modifying theheat-transfer installation or its operating parameters.

Correspondingly, these preferred compositions are particularlyappropriate for all the applications in which HCFC-123 is generallyused. Thus it is that these preferred compositions are particularlyappropriate for use as heat-transfer fluids in heat-transferinstallations comprising centrifugal compressors and in particulardirect-drive centrifugal compressors. These compressors are moreefficient and less expensive than compressors with a change-speed box.

The centrifugal compressors can be driven by an electric motor, a steamturbine, a gas turbine, a heat engine or other.

Preferably, the speed of sound obtained is close to that obtained withHCFC-123 and/or the volumetric capacity obtained is close to thatobtained with HCFC-123 and/or the operating pressure in the condenser isclose to that obtained with HCFC-123.

Thus, the compositions preferred above can make it possible to retain aconstant speed of rotation of the compressor during the replacement ofthe HCFC-123.

Likewise, these preferred compositions are particularly appropriate foruse as heat-transfer fluids in heat-transfer installations comprising aflooded evaporator.

Furthermore, these preferred compositions are particularly appropriatefor use in air conditioning, for example with a temperature in theevaporator of approximately 7° C. and a temperature in the condenser ofapproximately 35° C., and in installations with average power rangingfrom 250 kW to 35 MW.

The compositions according to the invention can also be used as blowingagent, propellant (for example for an aerosol), cleaning agent orsolvent, in addition to their use as heat-transfer fluids.

As propellant, the compositions according to the invention can be usedalone or in combination with known propellants. The propellantcomprises, preferably consists of, a composition according to theinvention. The active substance which has to be ejected can be mixedwith the propellant and inert compounds, solvents or other additives, inorder to form a composition to be ejected. Preferably, the compositionto be ejected is an aerosol.

As blowing agent, the compositions according to the invention can beincluded in a blowing composition, which preferably comprises one ormore other compounds capable of reacting and of forming a foam orcellular structure under appropriate conditions, as is known to a personskilled in the art.

In particular, the invention provides a process for the preparation ofan expanded thermoplastic product comprising first the preparation of apolymeric blowing composition. Typically, the polymeric blowingcomposition is prepared by plasticizing a polymer resin and by mixing inthe compounds of a blowing agent composition at an initial pressure. Theplasticizing of the polymer resin can be carried out under the effect ofheat, the polymer resin being heated in order to soften it sufficientlyto mix in a blowing agent composition. Generally, the plasticizingtemperature is close to the glass transition temperature or to themelting point for the crystalline polymers.

Other uses of the compositions according to the invention comprise theuses as solvents, cleaning agents or others. Mention may be made, forexample, of vapor degreasing, precision cleaning, the cleaning ofelectronic circuits, dry cleaning, abrasive cleaning, solvents for thedeposition of lubricants and release agents, and other solvent orsurface treatments.

The invention claimed is:
 1. A composition consisting essentially of2,4,4,4-tetrafluorobut-1-ene and cis-1,1,1,4,4,4-hexafluorobut-2-ene. 2.The composition as claimed in claim 1, consisting of a mixture of2,4,4,4-tetrafluorobut-1-ene and cis-1,1,1,4,4,4-hexafluorobut-2-ene. 3.The composition as claimed in claim 1, consisting essentially of,relative to the o al weight of the composition from 5% to 70% of2,4,4,4-tetrafluorobut-1-ene and from 30% to 95% ofcis-1,1,1,4,4,4-hexafluorobut-2-ene.
 4. A heat-transfer fluid comprisingthe composition as claimed in claim
 1. 5. The heat-transfer fluid asclaimed in claim 4, in which the composition is quasi-azeotropic.
 6. Theheat-transfer fluid as claimed in claim 4, in which the composition isnonflammable.
 7. A heat-transfer composition comprising the compositionas claimed in claim 1 and also one or more additives chosen fromlubricants, stabilizing agents, surfactants, tracers, fluorescentagents, odorous agents, solubilizing agents and their mixtures.
 8. Aheat-transfer installation comprising a vapor compression circuitcontaining a composition as claimed in claim 1 as heat-transfer fluid.9. The installation as claimed in claim 8, comprising a centrifugalcompressor.
 10. The installation as claimed in claim 8, comprising aflooded evaporator.
 11. The installation as claimed in claim 8, chosenfrom mobile or stationary installations for heat-pump heating, airconditioning, refrigeration or freezing and Rankine cycles.
 12. Aprocess for heating or cooling a liquid or a body by means of a vaporcompression circuit containing a heat-transfer fluid, said processsuccessively comprising the evaporation of the heat-transfer fluid, thecompression of the heat-transfer fluid, the condensation of the heatfluid and the reduction in pressure of the heat-transfer fluid, in whichthe heat-transfer fluid is a composition as claimed in claim
 1. 13. Aprocess for reducing the environmental impact of a heat-transferinstallation comprising a vapor compression circuit containing aninitial heat-transfer fluid, said process comprising a stage ofreplacement of the initial heat-transfer fluid in the vapor compressioncircuit by a final transfer fluid, the final transfer fluid exhibiting alower GWP than the initial heat-transfer fluid, in which the finalheat-transfer fluid is a composition as claimed in claim
 1. 14. Theprocess as claimed in claim 13, in which the initial heat-transfer fluidis 2,2-dichloro-1,1,1-trifluoroethane.
 15. A solvent comprising thecomposition as claimed in claim
 1. 16. A blowing agent comprising thecomposition as claimed in claim
 1. 17. A propellant comprising thecomposition as claimed in claim
 1. 18. A cleaning agent comprising thecomposition as claimed in claim
 1. 19. The composition as claimed inclaim 1, which is quasi-azeotropic.
 20. A heat-transfer installationcomprising a heat-transfer composition as claimed in claim
 6. 21. Thecomposition as claimed in claim 1, consisting essentially of, relativeto the total weight of the composition, from 20% to 65% of2,4,4,4-tetrafluorobut-1-ene and from 35% to 80% ofcis-1,1,1,4,4,4-hexafluorobut-2-ene.
 22. The composition as claimed inclaim 1, consisting essentially of, relative to the total weight of thecomposition, from 25% to 60% of 2,4,4,4-tetrafluorobut-1-ene and from40% to 75% of cis-1,1,1,4,4,4-hexafluorobut-2-ene.
 23. The compositionas claimed in claim 1, consisting essentially of, relative to the totalweight of the composition, from 28% to 51% of2,4,4,4-tetrafluorobut-1-ene and from 49% to 72% ofcis-1,1,1,4,4,4-hexafluorobut-2-ene.
 24. A composition consisting of2,4,4,4-tetrafluorobut-1-ene and cis-1,1,1,4,4,4-hexafluorobut-2-ene.